using MeetingAssistant.Transcription;

namespace MeetingAssistant.Speakers;

internal sealed record SpeakerSampleSpan(
    string Speaker,
    TimeSpan Start,
    TimeSpan End,
    TimeSpan SpeechDuration,
    TimeSpan MaximumDuration,
    IReadOnlyList<TranscriptionSegment> Segments)
{
    public static SpeakerSampleSpan? Create(
        TranscriptionSegment segment,
        TimeSpan maximumDuration)
    {
        if (maximumDuration <= TimeSpan.Zero)
        {
            throw new ArgumentOutOfRangeException(
                nameof(maximumDuration),
                maximumDuration,
                "Speaker sample maximum duration must be greater than zero.");
        }

        var boundedEnd = Min(segment.End, segment.Start + maximumDuration);
        return boundedEnd > segment.Start
            ? new SpeakerSampleSpan(
                segment.Speaker,
                segment.Start,
                boundedEnd,
                boundedEnd - segment.Start,
                maximumDuration,
                [segment with { End = boundedEnd }])
            : null;
    }

    public bool TryExtend(
        TranscriptionSegment segment,
        out SpeakerSampleSpan extended)
    {
        extended = this;
        if (!string.Equals(Speaker, segment.Speaker, StringComparison.OrdinalIgnoreCase) ||
            segment.Start >= Start + MaximumDuration)
        {
            return false;
        }

        var boundedEnd = Min(segment.End, Start + MaximumDuration);
        if (boundedEnd <= segment.Start)
        {
            return false;
        }

        var uncoveredStart = segment.Start > End ? segment.Start : End;
        var additionalSpeechDuration = boundedEnd > uncoveredStart
            ? boundedEnd - uncoveredStart
            : TimeSpan.Zero;
        extended = this with
        {
            End = boundedEnd > End ? boundedEnd : End,
            SpeechDuration = SpeechDuration + additionalSpeechDuration,
            Segments = Segments.Append(segment with { End = boundedEnd }).ToList()
        };
        return true;
    }

    public TranscriptionSegment ToSegment()
    {
        return new TranscriptionSegment(
            Start,
            End,
            Speaker,
            string.Join(' ', Segments
                .Select(segment => segment.Text)
                .Where(text => !string.IsNullOrWhiteSpace(text))));
    }

    private static TimeSpan Min(TimeSpan left, TimeSpan right)
    {
        return left < right ? left : right;
    }
}